Cascade Refrigeration Defrosting Without Hot Water Temperature Drop
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Solution Overview
Problem
Combined cascade refrigeration cycle apparatuses face challenges in completing defrosting operations quickly while minimizing the temperature decrease of hot water flowing through a hot-water pipe, as existing systems either shorten defrost time at the cost of lowering hot water temperature or increase defrost time due to lack of a heat source.
Innovation Solution
The apparatus incorporates a housing with two high-temperature-side and two low-temperature-side refrigeration circuits, where the low-temperature-side refrigerant circuit releases heat in the cascade heat exchanger during defrosting, ensuring a heat source is available for rapid defrosting without significantly decreasing hot water temperature, and the pump can be stopped during defrosting to prevent unheated hot water outflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a reverse cycle defrosting system is used to complete defrosting quickly, then defrosting time is shortened, but the temperature of hot water decreases to lower than inlet temperature
Solution Approach 1:
The patent extracts the hot water heating function from the high-temperature-side refrigeration circuit during defrosting operations. By guiding the high-temperature refrigerant directly to the water-refrigerant heat exchanger without passing through the cascade heat exchanger, the system separates the defrosting function from the hot water heating function, allowing defrosting to occur while maintaining hot water temperature through alternative heating paths.
Solution Approach 2:
The patent introduces a four-way switching valve as an intermediary component that enables flexible routing of the high-temperature refrigerant. This valve acts as a mediator that can direct the refrigerant to either the cascade heat exchanger for normal operation or directly to the water-refrigerant heat exchanger for defrosting operations, resolving the conflict between defrosting speed and hot water temperature maintenance.
2Temperature
If a hot-gas defrosting system is used to maintain hot water temperature, then hot water temperature is maintained, but defrosting time increases
Solution Approach 1:
The patent implements a dynamic system where the routing of the high-temperature refrigerant can be changed in real-time based on operational requirements. The four-way switching valve enables the system to dynamically switch between normal heating mode and defrosting mode, optimizing both hot water temperature maintenance and defrosting speed according to actual conditions.
3Loss of time
If two cascade refrigeration cycles are provided to ensure heat source for defrosting, then defrosting can be completed quickly, but the structure of the apparatus becomes complex
Solution Approach 1:
The patent makes the high-temperature-side refrigeration circuit universal by enabling it to serve dual purposes: normal hot water heating and defrosting operations. Through the four-way switching valve, the same refrigeration circuit and heat exchangers are used for both functions, eliminating the need for separate defrosting systems and reducing overall apparatus complexity while maintaining fast defrosting capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for a short defrosting time while maintaining hot water temperature, preventing extreme temperature reduction and ensuring continuous hot water supply when needed, thus enhancing operational efficiency and user satisfaction.
Implementation Method 1
a cascade heat exchanger... The refrigerant discharged from the low-temperature-side compressor of the low-temperature-side refrigeration circuit is guided to the low-temperature refrigerant flow channel of the cascade heat exchanger, and generates condensation heat. This condensation heat is absorbed in the high-temperature refrigerant flow channel of the cascade heat exchanger in the high-temperature-side refrigeration circuit.
Implementation Method 2
Heat is released in the refrigerant-side flow channel of the water-refrigerant heat exchanger. Water or hot water inside the hot-water pipe connected to the water-side flow channel of the water-refrigerant heat exchanger is heated.
Data Source
AI summary
According to one embodiment, an apparatus includes a housing, two high-temperature-side refrigeration circuits and two low-temperature-side refrigeration circuits. Each of the high-temperature-side refrigeration circuits is configured to exchange heat with both of the two low-temperature-side refrigeration circuits by cascade heat exchangers. A hot-water pipe letting water or hot water through water-refrigerant heat exchangers of the high-temperature-side refrigeration circuits is provided. When the low-temperature-side refrigeration circuit conducts a defrosting operation of the evaporator, the low-temperature-side refrigeration circuits are controlled in such a way that the low-temperature-side refrigerant circuit releases heat in the cascade heat exchanger.